hi got a TT system which currently has an old voltage trip. no chance of pme. wanna add a 2way consumer unit for the sockets and shower with a 30mA RCD. Gonna put in a 100mA RCD to replace the trip. Does this one need to be time delayed?
time delay or not?
- Thread starter oohthatslive!!
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The point of a delayed RCD, is that you can protect other circuits (especially those that can reasonably be expected to be used with portable equipment outdoors) with 30mA RCDs to cut power quiclky in the event of a fault leading to earth leakage.
With a Delayed RCD on your main supply, such a trip will allow he faulty circuit to be cut without cuting power to the rest of your installation. this is very convenient. If you have a 100mA RCD on your main supply without delay, then it will usually trip at the same time as the 30mA RCD, so you will lose all power. This not only inconvenient, but can be dangerous if you are e.g. up a ladder, running dowsntairs, lifting a heavy object, carrying a hot cooking pan.
p.s. what makes you say "no chance of pme?"
With a Delayed RCD on your main supply, such a trip will allow he faulty circuit to be cut without cuting power to the rest of your installation. this is very convenient. If you have a 100mA RCD on your main supply without delay, then it will usually trip at the same time as the 30mA RCD, so you will lose all power. This not only inconvenient, but can be dangerous if you are e.g. up a ladder, running dowsntairs, lifting a heavy object, carrying a hot cooking pan.
p.s. what makes you say "no chance of pme?"
yea thats wot i thought. cheers . already enquired about pme
You can put the time delayed RCD in the same position as the existing ELCB. I don bother doing this, just get a time delayed 100mA RCD to match your split load board and put in to replace the existing incomer.
Just one set of tails from the meter to the board then..
Just one set of tails from the meter to the board then..
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Providing that your existing CU is not metal 
thing is that the existing CU is just a 4 way wylex with sockets, lights, cooker and immersion heater. then theres anothere 2 way with with 2 15A fuses for storage heaters and then yet another 1 way with a 15A fuse for another storage heater. There is a 30mA RCD which feeds those heaters. Not sure why the storage heaters should be RCD protected! So as you can see there is a lot going on. Theres no electric shower so basically i just want to take the ring main off and put onto its own 30mA RCD circuit and separate the kitchen ring from the rest of the house. Any one have any ideas of the cost of this set up? TD RCD's seem quite pricey. Cheers
oohthatslive!! said:
Thats why you have and need an RCD. You cant achieve the fuse trip times with an earth rod so you will need:
100mA Time delayed RCD. use this to replace the old ELCB.
Retain the storage rad stuff. you could keep ts 30mA RCD if you want to.
Install new split load consumer unit for the rest of the house with ALL socket circuits on the 30mA RCD side. Thats it.
yea i know that. by the way i am getting readings of between 330 and 440 ohms for EFLI depending on the weather! NICEIC recommend 200 max. if i cant get it under wot do i do? just record the result? everythings on an RCD anyway
i thought the IEE reccomended 200 max (to be changed to 100 in the next edition of the regs) and the NICEIC reccomended 100 max.
as for how to get it down there are a few options:
1: join on another section of rod and hammer it deeper
2: fit a second rod (for best results try and keep the rods appart)
3: use some other type of earth electrode, if you are digging a trench for any other reason consider dropping in a peice of hard drawn copper wire of appropriate thickness (i think 16mm is the minimum but i'm not sure off hand) to act as an earth electrode.
also you might want to do a proper rod test as well as an EFLI test in case the eath at the suppliers end is shot (theirs is supposed to be below 20 ohms iirc).
as for how to get it down there are a few options:
1: join on another section of rod and hammer it deeper
2: fit a second rod (for best results try and keep the rods appart)
3: use some other type of earth electrode, if you are digging a trench for any other reason consider dropping in a peice of hard drawn copper wire of appropriate thickness (i think 16mm is the minimum but i'm not sure off hand) to act as an earth electrode.
also you might want to do a proper rod test as well as an EFLI test in case the eath at the suppliers end is shot (theirs is supposed to be below 20 ohms iirc).
yea i will put in another rod and test the Ze etc. but wot if i cant get it lower? not much i can do about it is there?
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YES! Fit another rod or replace the existing one with another in a better area. By better I mean the ground being less dry, rocky etc, so there is a better connection with the literal earth.
You don't need a split-load board...You could have two seperate units fed independently, one with 100mA G type & the other with 30mA G type.
You don't need a split-load board...You could have two seperate units fed independently, one with 100mA G type & the other with 30mA G type.
heres a piccy of wot i got at the moment
just gonna add a 2 way for kitchen ring and rest of sockets
just gonna add a 2 way for kitchen ring and rest of sockets
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